1. Field of the Invention
The present invention relates to a device for controlling an internal combustion engine as well as to a method of controlling the same. More specifically, the present invention relates to a device for and a method of controlling ignition timing when a richer air/fuel ratio is temporarily required.
2. Description of the Related Art
OTP (Over Temperature Protection) fuel increment control is generally implemented for preventing overheating of an exhaust system under high-loading and high-temperature conditions of an internal combustion engine (see for example, JAPANESE PATENT LAYING-OPEN GAZETTE No. S59-201950). Although the temperature of the internal combustion engine is generally determined by detecting the temperature of cooling water, the OTP fuel increment control detects operating conditions of the internal combustion engine and increases the fuel injection amount prior to detection of an increase in temperature of cooling water. When an accelerator pedal is depressed to place a throttle valve in a position exceeding a predetermined level, the OTP control system anticipates the high-loading and high-rotating speed operation of the internal combustion engine, which causes an increase in the temperature of the internal combustion engine, and increases the fuel injection amount.
The conventional OTP control system can prevent the undesirable temperature increase of the internal combustion engine and the exhaust system. The temperature of the internal combustion engine and the exhaust system does not, however, actually rise immediately after the operating condition of the internal combustion engine reaches a specific level. A proposed improvement of the OTP control accordingly does not execute the increment control immediately after the internal combustion engine is placed under the operating condition which leads to the high-loading and high-temperature condition, but increases the fuel injection amount after a predetermined delay time.
A knock control system has also been proposed, wherein a knock sensor for detecting knocking is mounted on the internal combustion engine. The knock control system advances the ignition timing by a certain degree when knocking is not detected for a certain time period whereas it retards the ignition timing by a certain degree when knocking is detected, thereby enhancing the power of the internal combustion engine. When the operating condition of the internal combustion reaches a predetermined level requiring an increment control of the fuel injection amount and the increment control of the fuel injection amount is implemented after a predetermined delay time, knocking is frequently observed during the delay time when the engine is under the high-loading condition. The ignition timing is then corrected in the retarding direction by the knock control.
The conventional control system, however, can not control the ignition timing appropriately at the start of the increment correction of the fuel injection amount after elapse of the predetermined delay time. The increment correction of the fuel injection amount after the predetermined delay time effectively reduces knocking and regulates the ignition timing in the advancing direction. The ignition timing control with the knock sensor repeats the correction of the ignition timing by a certain degree in the advancing direction when no knocking is observed for a certain time period. Such control causes a time lag between the actual reduction of knocking and the advance of the ignition timing to an appropriate level.